Investigation of off-aligned exchange coupling by torque curve and ferromagnetic resonance

Off-aligned exchange coupling in bilayer thin film is investigated by torqu e curve and ferromagnetic resonance (FMR). In off-aligned exchange coupling , the unidirectional anisotropy axis makes an angle beta with the anisotrop y axis of the ferromagnetic layer. The torque curves of the off-aligned exc hange are shifted with respect to the ones of the aligned case (beta =0). F rom the experimental measure of the shift angle alpha (0) and of the torque curve slope at alpha (0), one can determine independently the exchange ani sotropy field H-E and beta values. A description of the FMR modes in such a n off-aligned exchange coupling is given. The FMR mode position and linewid th are studied as a function of the anisotropy fields, of the off-aligned a ngle values, and of the applied field direction. The resonance frequency an d frequency linewidth present particular features which will help to do the right interpretation of FMR spectra of these systems. (C) 2001 American In stitute of Physics.